Americans Hate Tingle: This show has quite a few vocal detractors in the United States, especially since Canadian cartoons in general tend to do poorly in the USA anyway. The fact that it was Adored by the Network (despite getting terrible ratings) has been major fuel for it.
Ass Pull: One of the more frequent complaints is about the constant out of nowhere plot developments. "Johnny's 100th Episode" is a particular standout as Mr. Mittens and Dark Vegan's reasons for wanting Johnny to come out of his coma come completely out of nowhere.
Awesome Music: Dukey's Johnny Applesauce Song is a catchy folk song.
Base-Breaking Character: Believe it or not, Johnny himself. Some people see him as a Butt-Monkey and/or even somewhat of a woobie due to his horrid father and slightly crapsack life, while others hate him since he can be very whiny or despicable on occasion. Bling Bling Boy also has a following due to his meme status.
Broken Base: Similar to The Fairly OddParents, many people argue when the show went downhill. Exactly when did the series started going downhill? Was it early at Seasons 2-3, later at Seasons 4-6, or just at Seasons 5-6?
On one hand season 2 makes sense since the animation took a massive dip, and the music changed to just the same repetitive cues, and the writing and pacing felt a bit different.
Season 3 also makes sense since the animation became that of mostly rigging (but still alright) Warner Bros leaving production leaving Cookie Jar in charge, and the faster pacing than season 2, oh and the whipcracks starting.
Season 4, because the animation took another dip with less expressive and cartoony stuff, and flanderization started.
Season 5 & 6 also cause around this time, the series had been getting quite overaired, leading to many viewers' annoyance, not to mention this is when the aftermentioned whipcracks started to become more rampit, with it playing basically every single time someone moved a bodypart (mostly arms and hands), and it also reusing a-lot of plots from previous episodes or just having pretty ridiculous plots in general.
Cliché Storm: This show is criticized for rehashing a lot of stock cartoon plots, including its own.
Condemned by History: Believe it or not, the show was actually fairly popular during its first few years having a higher budget and completely different production team, not to mention Kids' WB! having a hand in its production (alongside the Canadian network Teletoon), probably helped. When Teletoon and Cookie Jar Entertainment took on the sole responsibility of production after Kids WB died out in 2008 (Warner Bros. still owns copyright and trademarks), the show's quality began to drop severely and many members of the notorious online "cartoon community" helped fuel hatred of the show. Not helping was the fact that it continued production well into 2014, mainly because of CanCon policies requiring all Canadian television stations to have a certain amount of natively produced content, which allowed the producers to continue the show (due to how cheap it was to make compared to other series) in spite of its abysmal ratings, as well as the show's oversatuation on both Teletoon and Cartoon Network. The series ended with little fanfare after TV producer David Straiton filed a lawsuit against series creator Scott Fellows (who at that point had zero involvement with the show) for not crediting him as a co-creator. While not as universally reviled today, it remains deeply unpopular with a majority of animation fans overall.
Critical Backlash: While the show still maintains a very large hate fanbase, it's slowly starting to fall under this trope as well. While it isn't a bad show, people who watched it after hearing about the immense amount of hate it gets tend to have this reaction. Some episodes are enjoyable, but the show itself just had the unfortunate timing of being a flawed-but-decent cartoon that became Adored by the Network while Cartoon Network was starting to undo its years of Network Decay.
Critic-Proof: The show's detractors will tell you that it's one of the worst cartoons ever made; the show itself ran for six seasons, with two more on the way.
Designated Hero: One of the main flaws of the show, especially for the fans themselves, is that it's nearly impossible to root for any of the main characters at times given how shallow and unlikable they are.
Dukey, despite being the more level-headed one, isn't exempt from this either. While he does point out when Johnny is about to do something stupid and/or irresponsible, he's perfectly willing to join in with his friend's antics (And, if not, he's easily bribed with meat). One episode even had Dukey blatantly distracting Johnny from getting his schoolwork done causing Johnny to have to do extra credit (so he wouldn't have to go to summer school). Another infamous episode featured Dukey acting like a Jerkass dog (Including chewing up the sisters' belts and eating their food) causing said sisters' to invent an obedience collar for him to get him under control (albeit using him as a servant). In the end, it's Susan and Mary who end up being punished and Dukey and Johnny mock them for it. Again, Dukey is portrayed as a Karma Houdini here. Not once is Dukey called out or punished for essentially putting Johnny in that situation in the first place (It's also Out of Character for Dukey since he's often the more responsible one of the two).
Susan and Mary are as likely as Johnny to put themselves, their family, and the world in danger with their inventions, and usually Johnny is the one who ends up fixing it.
Designated Villain: The hotel manager from "Johnny Test in 3-D". We're supposed to see him as a villain due to him repeatedly wanting to expose Dukey to Hugh and Lila, but considering that the hotel has a strict "no dogs" policy, it's not hard to side with him.
Escapist Character: Johnny's clearly meant to be this for the show's target audience; "Got a head of fiery hair, and a turbo-charged backpack" indeed. It... doesn't really work.
Evil Is Sexy: C'mon admit it, while they may be cute at least, you thought this when Susan and Mary transformed themselves into vampires. This applies a bit to their their faux supervillain personas as well
Foe Yay: Bumper does this with Johnny a lot, whether or not Johnny is crossdressing; one such example was in "Who's Johnny?" where Johnny tries to change his personality in one of his sisters' machines and, when he's stuck a smooth-talking British personality, Bumper implies to like this version of him a lot.
Whipcrack and guitar riff, because of how the show abuses these two sound effects every chance it gets. In this compilation of whipcracks (190 in one episode), half of the comment section is people joking that the whipcracks are actually recordings of the animators being forced to work on the show.
A meta-example. People sometimes use this show to prove that all Canadian animation is terrible. What many people don't know is that creator Scott Fellows and James Arnold Taylor (Johnny's voice actor), along with many of the show's writers, are Americans. Furthermore, American networks were all heavily involved in co-producing the series alongside Teletoon, with Kids' WB! working on the early seasons and Cartoon Network working on the later ones, meaning the show isn't even entirely Canadian.
Many detractors point their hatred for the show as being a copycat because it's too similar to Dexter's Laboratory. While that was a point of contention when it originally premiered, a good number of viewers were willing to look past it, as it was different enough not to be a carbon copy, and even welcomed it due to said similarities since Dexter had long since stopped airing. The true reason why it was hated was because Cartoon Network and Teletoon went overboard on broadcasting it, especially when it was used as a replacement for DC Nation in the U.S (which also suffered from CN's wonky programming schedule, and would ironically premiere the next overplayed series, Teen Titans Go!). By this point, viewers had gotten sick of the constant airings and detractors started listing any faults they could find to make it look like it was one of the worst cartoons ever.
She-Johnny appeared for about a second in the very first episode, but that was enough to grant an awful lot of fanart; in fact, look it up on DeviantArt or a related site.
Vampire Susan and Mary, especially among the anti-Twilight fans. The gothic dresses they wear, and their creepy, yet charming dialogue helps.
Joni West seems to be this, in fact she was so loved that she returned in The Lost Web Series.
Only the Creator Does It Right: The first season had a completely different production team from the rest of the series, and while considered average, it's still held in higher regard than the rest of the series.
Seasonal Rot: Season 1 is pretty decent, and potential it showed, but things went a little bit downhill in Seasons 2 and 3, though not too bad and still had Scott mostly involved, and the comedy was mostly the same, then Season 4 saw a bigger dip in quality, with the pacing becoming way too fast and much more nosier, which was taken up to another level in seasons 5 and 6, when the infamous whip-crack sound started playing when a character moved one of their body parts..
Shallow Parody: Quite a few, considering how little originality the show has.
One notable example is "The Hungry Games", which is yet another racing episode, so the government-orchestrated fight between minors has been downgraded to... a race for a pizza. Not just any pizza, but the last pizza in town. And the episode ends with Johnny giving a preachy lecture about sharing.
"Johnny Re-Animated" has Dawg & Bone, a parody of Johnny Test itself.
Johnny and Sissy look like siblings. Aside from that most likely unintentional instance, there's the writers' apparent fondness for Screw Yourself and everything related to it.
The scene after the beginning minutes of "Johnnyitis" in which Johnny, desperate to become sick in order to have an excuse to miss a big history test, eats a sick woman's used tissue. Said woman also had snot draining from her nose.
They Copied It, So It Sucks!: The show shares more than a few similarities to Dexter's Laboratory, granted folks noticed this right from the off way back in season one and, as mention in Misblamed, did think the show was copying but cited it different enough. Still the more hardcore detractors see it as a fault for the following:
Susan and Mary Test are obviously the Dexters of the show, being redheaded genius children with a laboratory in their house.
Johnny is like Dee Dee, since both of them are Dumb Blonde annoyances who constantly cause trouble for their genius siblings.
Their parents are kind of like if one took Dexter's mom and dad and swapped their personalities, and then Flanderized them: Johnny's Dad is a major neat-freak, while Dexter's Mom had her moments of this; Johnny's Mom is the head of the house and always working, while Dexter's Dad was just the head of the household.
Also, a female in the main cast is bothered by an Abhorrent Admirer, who is another nerdy genius child with their own laboratory; Bling-Bling Boy is the Mandark of the show.
Dukey can also be compared to Monkey, both being animals who have gained unusual abilities because of the genius children, Dukey's being talking while Monkey becomes a superhero.
Let's not forget that there was also an episode of Dexter's Lab called "Dexter's Lab", in which Dexter finds a lost dog that he teaches to speak English.
Not helping the show's case, the concept for Johnny Test was supposedly created in 1995. In other words, shortly after the first episode of Dexter's Laboratory aired in February 1995.
They Wasted a Perfectly Good Character: One criticism is that a majority of the episode are Johnny focused and his antics that affect others. But rarely give the spotlight to any of the other characters outside him. Yeah there are subplots on occasion (Susan and Mary's attempts to woo Gil for one), but they hardly pop up in later seasons,
Uncanny Valley: Speed McCool and Monkey, although that's probably intentional, considering the two are based on old action cartoons.
The animation after Season 1 falls into this.
We're Still Relevant, Dammit!: Probably the worst example of this would be the YouTube (or rather, "Snoobtube") episode... in 2010. In fact, looking up the website redirects the user to Nick.com. Coincidentally, Nick is also known for trying to be hip with the kids.
What an Idiot!: Johnny's idea to replace toy cereal prizes with real, lethal laser guns for kids in Johnny-O's isn't a good idea, as you could probably tell.
The Woobie: Dukey, who always seems to get frozen in a block of ice or turned to stone. Also, the episode "Bathtime for Johnny", where Johnny "forgot" his birthday and he sobbed his heart out for nearly the whole episode. Last but not least, most people go out of their way in the show to point out how ugly he is.